Q195 Carbon Steel: Low-Carbon Mild Steel for General Structural and Forming Applications
Q195 carbon steel, designated under the Chinese GB standard (equivalent to ASTM A283 Grade C or JIS G3101 SS330), is a low-carbon mild steel widely utilized for its excellent formability, weldability, and cost-effectiveness. With a carbon content of ≤0.12%, Q195 offers moderate strength (tensile strength ≥315 MPa) while maintaining superior ductility, making it ideal for cold heading, deep drawing, and general structural applications. This article explores its chemical composition, mechanical properties, manufacturing processes, and key industrial applications.
1. Chemical Composition (GB/T 700 Standard)
| Element | Content Range | Function |
|---|---|---|
| Carbon (C) | ≤ 0.12% | Low carbon ensures high ductility and weldability; minimizes hardening during cold working |
| Manganese (Mn) | 0.25 – 0.50% | Improves strength and deoxidation; enhances hot working performance |
| Silicon (Si) | ≤ 0.30% | Deoxidizer; improves surface quality during hot rolling |
| Phosphorus (P) | ≤ 0.045% | Impurity; controlled to prevent cold brittleness |
| Sulfur (S) | ≤ 0.050% | Impurity; limited to avoid hot shortness during rolling |
| Copper (Cu) | ≤ 0.25% | Residual element; excessive content may affect surface quality |
2. Mechanical Properties (Room Temperature)
- Tensile Strength (σb): 315 – 430 MPa (varies by thickness; higher for thinner sections)
- Yield Strength (σs): ≥ 195 MPa (minimum guaranteed for structural integrity)
- Elongation (δ5): ≥ 33% (excellent for cold forming and deep drawing operations)
- Brinell Hardness (HB): ≤ 137 (soft material suitable for machining and stamping)
- Bend Test: 180° cold bend with d=0 (no cracks; demonstrates superior formability)
3. Manufacturing Process Overview
- Steelmaking: Basic oxygen furnace (BOF) or electric arc furnace (EAF) with ladle refining to achieve low carbon and impurity levels. Aluminum or silicon is used for final deoxidation to produce killed or semi-killed steel.
- Continuous Casting: Cast into billets or slabs with controlled cooling to prevent internal defects. Typical section sizes: 100×100mm to 160×160mm for billets, 120-250mm thickness for slabs.
- Hot Rolling: Reheated to 1100-1250°C and rolled in multiple passes to achieve final dimensions (e.g., 1.5-20mm for sheets, 5.5-25mm for rounds). Controlled cooling prevents grain coarsening.
- Cold Rolling (for thin sheets): Cold reduction by 30-70% to achieve thicknesses below 3mm, followed by annealing at 650-700°C to restore ductility.
- Surface Treatment: Pickling (hydrochloric or sulfuric acid) to remove oxide scale; oiling or phosphating for temporary corrosion protection during storage.
4. Key Application Fields
Construction & Structural
Light structural frameworks, reinforcement mesh, roofing sheets, and temporary scaffolding. Complies with GB 50017 for steel structure design in non-corrosive environments.
Automotive Components
Body panels, fuel tanks, exhaust system brackets, and interior support structures. Preferred for its deep drawability in stamping operations (e.g., door panels, fenders).
Wire & Fasteners
Low-carbon wire rod (Φ5.5-14mm) for nails, staples, and cold-headed bolts (Grade 4.6/4.8). Excellent for high-speed wire drawing due to minimal work hardening.
Home Appliances & Furniture
Washing machine drums, refrigerator cabinets, metal furniture frames, and HVAC ductwork. Easily formed into complex shapes with minimal springback.
Packaging Industry
Steel drums (≤200L), pails, and strapping bands. Compatible with tinplating or galvanizing for enhanced corrosion resistance in packaging applications.
General Engineering
Shims, gaskets, and non-critical machinery parts. Often used as base material for case hardening (carburizing) to improve surface wear resistance.
5. Comparison with Similar Low-Carbon Steels
| Grade | Standard | Carbon Content | Tensile Strength | Primary Use |
|---|---|---|---|---|
| Q195 | GB/T 700 | ≤ 0.12% | 315-430 MPa | Deep drawing, cold heading, general structural |
| Q215 | GB/T 700 | 0.09-0.15% | 335-450 MPa | Structural tubes, light load-bearing components |
| SPCC (SS330) | JIS G3141 | ≤ 0.15% | ≥ 270 MPa | Cold-rolled sheets for automotive panels |
| ASTM A36 | ASTM A36/A36M | ≤ 0.26% | 400-550 MPa | Heavy structural plates, bridges, buildings |
| DC01 | EN 10130 | ≤ 0.12% | 270-410 MPa | Cold forming, deep drawing (European equivalent) |
6. Selection Guidelines & Processing Recommendations
- Forming: Optimal for cold forming with a minimum bend radius of 0T (thickness). Use lubricants (e.g., mineral oil) to reduce galling in deep drawing operations.
- Welding: Easily weldable with SMAW (E6013 electrode), GMAW (ER70S-6 wire), or resistance welding. Preheating not required for sections ≤20mm.
- Machining: Low carbon content results in gummy chips; use high-speed steel (HSS) tools with positive rake angles. Surface speed: 25-35 m/min for turning.
- Heat Treatment: Normalizing at 880-940°C to refine grain structure if hot-worked. Avoid quenching to prevent distortion.
- Corrosion Protection: Apply zinc coating (galvanizing) or paint systems for outdoor applications. Not suitable for untreated use in humid or chloride-rich environments.
- Quality Certification: Verify mill test certificates (MTC) per GB/T 20066, including chemical analysis, mechanical properties, and ultrasonic testing for critical applications.
7. Request a Carbon Steel Quote
For customized Q195 carbon steel products—including hot-rolled coils, cold-rolled sheets, wire rods, or structural sections—contact Baoli Iron & Steel for competitive pricing and technical support. Our inventory includes standard and non-standard dimensions with optional surface treatments (pickled, oiled, or galvanized) to meet your project requirements.